Leveraging its full-industry-chain advantages, vertical integration, and massive proprietary R&D, BYD has achieved global leadership in new energy vehicle sales. To address the growing complexity of vehicle systems while sustaining this leadership, systematic application of systems engineering methods has become essential across the product lifecycle. This keynote focuses on digital engineering practices with Modelica, exploring three interrelated areas: 1) co-simulation design and validation methodologies for highly integrated vehicle systems; 2) high-fidelity and computationally efficient modeling approaches for diverse R&D scenarios; and 3) engineering implementation of toolchain integration and virtual validation. We are currently advancing Modelica-based digital engineering practices across multiple domains: developing a whole-vehicle digital engineering co-simulation platform that integrates powertrain, thermal management, and chassis control models, realizing seamless cross-system collaborative optimization of power performance, energy efficiency, and handling stability; creating digital models for HVAC thermal management systems that accurately predict cabin thermal load and system power consumption and energy flows, significantly enhancing both energy efficiency and cabin comfort; implementing digital development processes for seat systems that enable early-stage validation of control strategies, vibration-noise characteristics, and comfort attributes through model-driven design and simulation, substantially reducing physical prototype development-cycles; and pioneering AI-Modelica integration that leverages data-driven methods to accelerate model generation, parameter identification, and calibration, substantially improving the intelligence level of complex system modeling. These practices collectively validate Modelica’s critical role in complex multidisciplinary system modeling, offering a new paradigm for enhancing research and development efficiency in intelligent vehicle development.